Force_Spring.cpp

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/*
===========================================================================

Doom 3 GPL Source Code
Copyright (C) 1999-2011 id Software LLC, a ZeniMax Media company. 

This file is part of the Doom 3 GPL Source Code (?Doom 3 Source Code?).  

Doom 3 Source Code is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Doom 3 Source Code is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Doom 3 Source Code.  If not, see <http://www.gnu.org/licenses/>.

In addition, the Doom 3 Source Code is also subject to certain additional terms. You should have received a copy of these additional terms immediately following the terms and conditions of the GNU General Public License which accompanied the Doom 3 Source Code.  If not, please request a copy in writing from id Software at the address below.

If you have questions concerning this license or the applicable additional terms, you may contact in writing id Software LLC, c/o ZeniMax Media Inc., Suite 120, Rockville, Maryland 20850 USA.

===========================================================================
*/

#include "../../idlib/precompiled.h"
#pragma hdrstop

#include "../Game_local.h"

CLASS_DECLARATION( idForce, idForce_Spring )
END_CLASS

/*
================
idForce_Spring::idForce_Spring
================
*/
idForce_Spring::idForce_Spring( void ) {
        Kstretch                = 100.0f;
        Kcompress               = 100.0f;
        damping                 = 0.0f;
        restLength              = 0.0f;
        physics1                = NULL;
        id1                             = 0;
        p1                              = vec3_zero;
        physics2                = NULL;
        id2                             = 0;
        p2                              = vec3_zero;
}

/*
================
idForce_Spring::~idForce_Spring
================
*/
idForce_Spring::~idForce_Spring( void ) {
}

/*
================
idForce_Spring::InitSpring
================
*/
void idForce_Spring::InitSpring( float Kstretch, float Kcompress, float damping, float restLength ) {
        this->Kstretch = Kstretch;
        this->Kcompress = Kcompress;
        this->damping = damping;
        this->restLength = restLength;
}

/*
================
idForce_Spring::SetPosition
================
*/
void idForce_Spring::SetPosition( idPhysics *physics1, int id1, const idVec3 &p1, idPhysics *physics2, int id2, const idVec3 &p2 ) {
        this->physics1 = physics1;
        this->id1 = id1;
        this->p1 = p1;
        this->physics2 = physics2;
        this->id2 = id2;
        this->p2 = p2;
}

/*
================
idForce_Spring::Evaluate
================
*/
void idForce_Spring::Evaluate( int time ) {
        float length;
        idMat3 axis;
        idVec3 pos1, pos2, velocity1, velocity2, force, dampingForce;
        impactInfo_t info;

        pos1 = p1;
        pos2 = p2;
        velocity1 = velocity2 = vec3_origin;

        if ( physics1 ) {
                axis = physics1->GetAxis( id1 );
                pos1 = physics1->GetOrigin( id1 );
                pos1 += p1 * axis;
                if ( damping > 0.0f ) {
                        physics1->GetImpactInfo( id1, pos1, &info );
                        velocity1 = info.velocity;
                }
        }

        if ( physics2 ) {
                axis = physics2->GetAxis( id2 );
                pos2 = physics2->GetOrigin( id2 );
                pos2 += p2 * axis;
                if ( damping > 0.0f ) {
                        physics2->GetImpactInfo( id2, pos2, &info );
                        velocity2 = info.velocity;
                }
        }

        force = pos2 - pos1;
        dampingForce = ( damping * ( ((velocity2 - velocity1) * force) / (force * force) ) ) * force;
        length = force.Normalize();

        // if the spring is stretched
        if ( length > restLength ) {
                if ( Kstretch > 0.0f ) {
                        force = ( Square( length - restLength ) * Kstretch ) * force - dampingForce;
                        if ( physics1 ) {
                                physics1->AddForce( id1, pos1, force );
                        }
                        if ( physics2 ) {
                                physics2->AddForce( id2, pos2, -force );
                        }
                }
        }
        else {
                if ( Kcompress > 0.0f ) {
                        force = ( Square( length - restLength ) * Kcompress ) * force - dampingForce;
                        if ( physics1 ) {
                                physics1->AddForce( id1, pos1, -force );
                        }
                        if ( physics2 ) {
                                physics2->AddForce( id2, pos2, force );
                        }
                }
        }
}

/*
================
idForce_Spring::RemovePhysics
================
*/
void idForce_Spring::RemovePhysics( const idPhysics *phys ) {
        if ( physics1 == phys ) {
                physics1 = NULL;
        }
        if ( physics2 == phys ) {
                physics2 = NULL;
        }
}